The present invention relates to a structure for securing an optical device and fiber optics, and, more particularly, to a structure for securing an optical device and fiber optics in a high accuracy.
An example of conventional structure for securing an optical device and fiber optics is described in Japanese Patent Application Laid-Open No. 8-201660 (hereinafter called the "first prior art"). According to the description, there is formed a V-groove in a substrate such as silicon, in which a termination of fiber optics is secured, while a light emitting device is secured on its optical axis, or Z-axis with relatively low accuracy.
Then, there is formed a V-groove on the Z-axis to cross it, in which a spherical lens is contained. The spherical lens is slid along the V-groove while operating the light emitting device to actually measure coupling with the fiber optics, thereby adjusting the light beam to an optimal state.
Another securing structure is described in Japanese Patent Application Laid-Open No. 3-158805 (second prior art). According to the description, fiber optics of which the end face is cut askew is mounted on the substrate formed with the V-groove, and the optical axis is refracted on that face to optically couple it to a surface incident light receiving device directly mounted on the plane of substrate.
Still another securing structure is described in Japanese Patent Application Laid-Open No. 6-138341 (third prior art). According to the description, a silicon guide plate is attached to a transparent substrate, and fiber optics is inserted into a guide hole.
However, the first prior art has a problem that the optical axis should be adjusted by operating the optical device to optically couple the optical device and the fiber optics. This is because the light emitting device is secured on the optical axis with a relatively low accuracy.
In addition, even if the optical device is secured with a high accuracy, it is necessary to position three optical axes of the fiber optics, the spherical lens, and the optical device with a high accuracy to obtain a high coupling efficiency. Therefore, a high optical coupling efficiency cannot be attained in the first prior art in which the spherical lens is mounted in the v-groove formed in the Z-axis to crossing it.
Furthermore, the first prior art also has a problem that a surface type optical device cannot be directly applied. It is because it is very difficult to place the surface of the optical device on a substrate such as silicon formed with the V-groove to cross the optical axis of the fiber optics (Z-axis). Therefore, in general, when a surface type optical device is mounted, it is necessary for the light receiving device 42 to be mounted on a carrier 41 as shown in a sectional view in FIG. 13, which shows a mounting structure of a prior art, so that the surface is caused to cross the optical axis (Z-axis). In this case, since the number of components is further increased, it becomes more difficult in practice to secure the optical axis without adjustment.
Then, since the second and third prior arts is to optically couple an optical device and fiber optics as in the first prior art, they have a problem that an optical axis should be adjusted while operating the optical device.
It is because the second prior art does not have a structure in which fiber optics and an optical device are uniquely positioned since it requires to control the direction of rotation or insertion position of the fiber optics to obtain a high optical coupling efficiency.
In addition, the third prior art is necessary to position a lens and an optical device with a high accuracy to obtain collimated light, so that no adjustment of the securing of optical axis is actually difficult.